Conventionally, for personal watercraft, an auto-cruise (automated cruise) mode has been disclosed, in which a motor controls a throttle valve for changing an amount of intake-air supplied to an engine under control of an ECU (electronic control unit) and the personal watercraft is driving at a constant speed automatically without depending on a rider's operation for opening and closing the throttle valve. In the auto-cruise mode, the operation performed by the rider can be reduced as compared to a normal mode in which the rider manually performs the operation for opening and closing the throttle valve.
When a body of the watercraft is skipping over water waves, a water intake provided on a bottom surface of a hull of the watercraft is exposed in air for a moment, decreasing a load applied on the engine. This may sometimes cause over revolution of the engine. Under this condition, if the auto-cruise mode is turned on, then the over revolution of the engine is maintained. To avoid this, a personal watercraft is configured to be inhibited from starting the auto-cruise mode irrespective of the rider's operation for turning on the auto-cruise mode, if the engine speed is higher than a preset upper limit value (see Japanese Laid-Open Patent Application Publication No. 2007-314084).
However, the rider may feel driving discomfort, because the auto-cruise mode is not started even though the rider has turned on the auto-cruise mode. For example, in a case where the rider turns on the auto-cruise mode while the watercraft is driving steadily, the auto-cruise mode is inhibited from being started if the body of the watercraft is above the water surface and the engine speed becomes higher than the preset upper limit value for a moment. This may force the rider to turn on the auto-cruise mode again.